1 H NMR Troubles. Even though this is a pure NMR spectrum of the listed compound

Question

1H NMR Troubles. Even though this is a pure NMR spectrum of the listed compound, the NMR data are not easy to interpret. There are two (2) significant issues/problems/complexities that make a complete analysis of this spectrum impossible: briefly explain using a minimum of words.

1H NMR Data. It will be difficult to process this NMR data in the style of the supplemental handouts titled Reporting NMR and IR Data and NMR Product Data Format; however, given the hints listed below, process this 1H NMR data and transform it into text data that is appropriate for inclusion at the end of the Procedure. Here are the hints:

Peak C in the 1H NMR spectrum corresponds to a single hydrogens type in the product that integrates to four hydrogens (4H); use this information to scale the other peaks accordingly.

Each aromatic peak can be considered a multiplet (“m”), and there is no need to list or tabulate coupling information (J-values).

Chemical shift (õ) values can be reported as an average of the centermost listed peaks, or as a range (most appropriate for peak A)

Extra H? What accounts for the “extra integral” (leftover H’s that are not part of the product) that you have uncovered in your analysis in Question 2.

Contaminants. (4 pts) Using this 1H NMR data, determine the identity and % composition of the contaminant compound(s) present in the spectrum. Justify your answer with pertinent chemical shift and splitting information.

Explanation / Answer

As indicated in question, this is a clean compound and spectra should be reported as follows

1H NMR (CDCl3, 400 MHz): 7.29-7.24 (m, 12H), 7.22-7.17 (m, 4H), 6.96-6.94 (m, 4H)

All peaks were considered as multiplets since there splitting pattern is not clean.

Spectra becomes complex if we dont have information about solvent residual peaks.

Extra hydrogen is from CHCl3 which is present in traces in CDCl3. This comes as a sharp singlet at 7.26 ppm. 64% contamination (3.64 (Observed integration) -3.00 (Expected integration) = 0.64; 0.64*100 = 64)

Another contaminant is water which also comes as a singlet at 1.56 ppm. 10% contamination (0.106 *100 = 10.6).

Peaks (triplet at 1.26 ppm and multiplet at 3.73 ppm) correspond to ethanol. 3% contamination (0.03 *100 = 3)

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